The purpose of this paper is to explore the effects of the addition of air to various automotive lubricating oils, and the resulting differences observed in aging characteristics of fluoroelastomer (FKM) vulcanizates.
In standard ASTM, full-immersion laboratory oil agings, a number of “SF” and “SG”-rated automotive lubricating oils have been shown to exhibit aggressive deterioration of the physical properties of fluoroelastomer vulcanizates. However, parts based on fluoroelastomer continue to provide excellent service life in actual end-use applications, even in those oils which laboratory tests indicate are too severe for practical FKM service.
The introduction of air during oil aging significantly reduces the extent of property loss of FKM vulcanizates. Thus, the apparent contradiction between laboratory, full-immersion oil aging, and actual, end-use performance may be reconciled to a large degree by the fact that ASTM, full-immersion tests simply do not adequately reflect the conditions of actual part service; in particular, the effect of air on the oil.
This paper summarizes the effects of air addition and oil temperature on the aging characteristics of various types of fluoroelastomer vulcanizates in a number of current automotive lubricating oils.